Existing RF transmitters can be classified mainly into two types: quadrature modulated transmitters or polar modulated transmitters. A conventional quadrature modulated RF transmitter typically includes a baseband digital signal processor (DSP),  two digital-to-analog converters (DACs), low pass filters (LPFs) for quadrature channels, a quadrature modulator, a variable gain amplifier (VGA) and a power amplifier (PA). A conventional polar modulated RF transmitter typically includes a baseband DSP, DACs and LPFs for the amplitude modulation path and phase modulation path. The phase modulation path changes carrier clock phases used in the amplitude modulation path. The amplitude modulation path creates a modulated RF signal. A proper delay is required to match the amplitude modulation path and the phase modulation path. A power amplifier enlarges the amplitude of the modulated RF signal.
Conventional RF transmitter architectures have a problem reaching good linearity and power efficiency simultaneously, as good linearity usually implies high power consumption, because the analog components operate as class A devices, resulting in poor power efficiency. In addition, active and passive components, such as filter capacitors and large transistors for minimizing flicker noise, occupy additional silicon area which increases cost. Furthermore, analog circuits are highly sensitive to process, temperature and supply voltage variation. Device matching is also a problem for deep submicron CMOS (Complimentary Metal Oxide Semiconductor) technologies. Because conventional RF transmitter architectures have separate modulator and power amplifier components, redundant areas are created in the modulator and the amplifier for the transmitter architectures. In addition, conventional digital quadrature modulators typically drive a 50 Ohm impedance, and thus power consumption tends to be relatively high at the modulator output. Non-linear distortion is also difficult to compensate for conventional power amplifiers and modulators, as they are located in different chips where the environments differ, and this gives rise to additional interference in the radio band. Since a power amplifier is not typically included as part of a conventional digital quadrature modulator, system integration is not optimized which further increases the cost of the final RF transmitter structure.